Monday, October 3, 2011

Ability Point Swapping and Experience Bonuses in Men & Magic

On p. 10 of
Men & Magic Gary Gygax explained how characters could use points from
another ability score to increase their score in the class prime requisite “for
purposes of gaining experience only.”
Though later editions—Holmes and Moldvay—had a mechanism for the actual
swapping of points, I think the consensus on what Gygax meant in Men &
Magic is that the mere existence of average to high scores in certain abilities
meant that one might get a bump up in one’s prime requisite for the purpose of
computing the experience point bonus or penalty. (Why I think this is the
consensus, and why I think the consensus is correct is another question, but I
do not intend to argue for it here.)

The experience point bonus/penalty numbers look like this:

Modified
Prime

Requisite
Score

Experience
Point

Bonus/Penalty

3-6

-20%

7-8

-10%

9-12

0

13-14

+5%

15+

+10%

All classes
have a prime requisite ability score and a secondary ability score. All except Magic-users have a tertiary
ability score. The chart below
summarizes things and includes the character class of Thieves from the first
supplement:

Class

Prime

Requisite

Secondary

Ability

Tertiary

Ability

Cleric

Wisdom

Intelligence

Strength

Fighter

Strength

Intelligence

Wisdom

Magic-user

Intelligence

Wisdom

None

Thief

Dexterity

Wisdom

Intelligence

Clerics,
Fighters and Magic-users can use their secondary score to add 1 point to their prime requisite (again, only for the purpose of computing the experience
bonus/penalty) for every 2 secondary score points above 9. Fighters and Clerics can add 1 point
for every 3 tertiary score points above 9. Thieves have slightly different rules—they can trade 1 secondary score points and 2 tertiary score points for 1 prime requisite
point. (Presumably this is a
package deal—if one’s secondary score was, say, 9 or below, one simply couldn’t trade in any tertiary points, even if one had a tertiary score of 18.)

For the heck
of it I created these charts:

Clerics—Bonus
Points Added to Wisdom

(For
Purposes of Gaining Experience Only)

↓Strength
Intelligence→

1-10

11

12

13

14

15

16

17

18

1-10

0

+1

+1

+2

+2

+2

+3

+3

+4

11

0

+1

+1

+2

+2

+2

+3

+3

+4

12

+1

+2

+2

+3

+3

+3

+4

+4

+5

13

+1

+2

+2

+3

+3

+3

+4

+4

+5

14

+1

+2

+2

+3

+3

+3

+4

+4

+5

15

+2

+3

+3

+4

+4

+4

+5

+5

+6

16

+2

+3

+3

+4

+4

+4

+5

+5

+6

17

+2

+3

+3

+4

+4

+4

+5

+5

+6

18

+3

+4

+4

+5

+5

+5

+6

+6

+7

Fighters—Bonus
Points Added to Strength

(For
Purposes of Gaining Experience Only)

↓Wisdom
Intelligence→

1-10

11

12

13

14

15

16

17

18

1-10

0

+1

+1

+2

+2

+2

+3

+3

+4

11

0

+1

+1

+2

+2

+2

+3

+3

+4

12

+1

+2

+2

+3

+3

+3

+4

+4

+5

13

+1

+2

+2

+3

+3

+3

+4

+4

+5

14

+1

+2

+2

+3

+3

+3

+4

+4

+5

15

+2

+3

+3

+4

+4

+4

+5

+5

+6

16

+2

+3

+3

+4

+4

+4

+5

+5

+6

17

+2

+3

+3

+4

+4

+4

+5

+5

+6

18

+3

+4

+4

+5

+5

+5

+6

+6

+7

Magic-users—Bonus
Points Added to Intelligence

(For
Purposes of Gaining Experience Only)

Wisdom→

1-10

11

12

13

14

15

16

17

18

0

+1

+1

+2

+2

+2

+3

+3

+4

Thieves—Bonus
Points Added to Dexterity

(For
Purposes of Gaining Experience Only)

↓Wisdom
Intelligence→

1-10

11

12

13

14

15

16

17

18

1-9

0

0

0

0

0

0

0

0

0

10

0

+1

+1

+1

+1

+1

+1

+1

+1

11

0

+1

+1

+2

+2

+2

+2

+2

+2

12

0

+1

+1

+2

+2

+3

+3

+3

+3

13

0

+1

+1

+2

+2

+3

+3

+4

+4

14

0

+1

+1

+2

+2

+3

+3

+4

+4

15

0

+1

+1

+2

+2

+3

+3

+4

+4

16

0

+1

+1

+2

+2

+3

+3

+4

+4

17

0

+1

+1

+2

+2

+3

+3

+4

+4

18

0

+1

+1

+2

+2

+3

+3

+4

+4

What this shows, among other things is that under what we might call the virtual point
swapping scheme, it’s pretty darn difficult to get a set of scores that will produce experience penalties, and conversely it is not very difficult to get a set of scores that will produce bonuses. This is due to the fact that even with a low "raw" prime requisite score, the odds are that you'll be saved by one or more bonuses from your secondary or tertiary scores.

Combining the above charts together with the bell-curve odds of the prime requisite score, here are the
odds for the range of experience bonuses and penalties for someone who, before rolling 3d6 in order, has it in his mind to choose a particular class:

Experience

Bonus/
Penalty

Cleric

Fighter

Magic-user

Thief

+10% or
better

20%

20%

19%

12%

+5% or
better

39%

39%

33%

31%

-10% or
worse

19%

19%

27%

23%

-20%

6%

6%

13%

8%

So if you know you want to play a particular class, there's a 30-40% chance you will roll up scores that will give you at least a small experience bonus and a 70-80% chance that you will avoid any experience penalty.But if you are prepared to play any of the four classes, then the odds of rolling up a character who gets
the highest experience bonus of +10% are better than even, and the odds of
rolling up a “hopeless” character who will suffer a penalty are extremely low—about 1 in 500 for the -10%
penalty and 1 in 30,000 for the -20% penalty!!!